Feder U.S. Pat. No. 3,229,002 was the outcome of development of a process for treating resin paricles, e.g. -35 mesh polyethylene, to improve the flowability of the particles so that the polyethylene would be better suited for use in injection molding and in the production of rug backings. Briefly, the treatment involves passing the resin through a drum in which a rotor having spaced blades or rods hurls the material into a dispersion. The material is heated by this action and this causes changes which improve the flowability.
Subsequently, the process was applied to the blending of various materials, e.g. pigments and waxes, with resin particles. That extension resulted in Feder U.S. application Ser. No. 772,894, filed Feb. 28, 1977, abandoned in favor of Ser. No. 240,441 filed Mar. 4, 1981 which in turn was abandoned in favor of Ser. No. 368,328, filed Apr. 14, 1982. Here again heating is utilized, as the heating causes the resin and the additive to coalesce.
More recently, attempts were made to apply the process to the treatment of reactor fluff or flake. The fluff is a polymer as it is produced in a reactor. The polymers of interest were polyethylene and polypropylene, particularly polyethylene. The polymer is in the form of particles of varying sizes. By reason of the variation in particles size, the fluff is not suitable for use by some converters.
In, for example, blow molding, the molder extrudes the polyethylene into a tube which is cut, and the resulting parts are molded by blowing. The fluff, with its great variation in particle size, is unsuitable for transportation to and use by the molder in his extruder. In the fluff, the small particles have a high melt index and the large particles have a low melt index. Apparently, these conditions, together with segregations with respect to particle size, render the fluff unsuitable for extrusion by the molder. To remedy that situation, the practice in the industry is that the prime producer of the polyethylene extrudes the fluff, and forms the extrusion product into pellets. The extrusion by the prime producer is a high power consumption operation, and, additionally, the accompanying heat causes some degradation.
Efforts were made to utilize the process and apparatus of the aforementioned patent to blend the large and small fluff particles, into particles composed of both the large and small particles. In the process of the Feder patent heat is utilized to effect the desired treatment, and in respect to the fluff the small particles stick to or melt onto the larger particles. The product produced from the fluff, while not of the uniform size which is usual for pellets, appeared to be quite adequate for the needs of the molder, while in the inventor's process power consumption is substantially less and there is no degradation.
However, the capacity which the prime producers require is much larger than can be provided by the present apparatus, i.e. the apparatus disclosed in the Feder patent. The problem could be dealt with by enlarging the size of the apparatus, but the size which would result would be such as to make the agitator unattractive to the prime producers.